In stormy winters like this, residents of drought-prone Southern California fret about how much rainfall flows into the ocean, a reminder of the amounts of water the region is wasting instead of saving for good use.

A new bill by a San Fernando Valley state senator aims to fix that.

The bill introduced Monday by Sens. Bob Hertzberg, D-Van Nuys, and Scott Wiener, D-San Francisco, would require huge reductions in the volume of treated wastewater discharged into the Pacific Ocean and California estuaries.

SB 332, the Local Water Reliability Act, calls on wastewater treatment facilities to step up recycling, conservation and efficiency to meet reduction targets of 50 percent by 2030 and 95 percent by 2040 for the amount of water dumped into the ocean.

“I introduced a bill on this exact subject nearly four years ago, and it pains me that nothing has improved,” Hertzberg, the Senate’s majority leader, said Tuesday in a statement. “It is backwards for Southern California to continue importing water by sticking a straw in the Colorado River, or in the North, while we’re also dumping billions of gallons of water into the ocean.

“The reality of climate change has led our society to shift toward sustainable and renewable electricity; we must rethink our water policy with the same view toward sustainability.”

But it’s likely to face criticism from some of the water agencies that opposed Hertzberg’s similar bill in 2015. Back then, opponents complained that water re-use mandates would saddle agencies with “staggering” costs. That bill died at the committee level.

Since then, California has taken several steps to promote recycling of wastewater, which includes both water from rain and water for household and commercial use.

Still, the backers of SB 332 said, most communities continue to use water once and dispose of it. Relying on a study by the environmental group Heal the Ocean, Hertzberg and Wiener said 1.1 billion gallons of treated water a day are discarded into the ocean and estuaries. That, they said, is enough to fill the Rose Bowl stadium 12 times a day.

Hertzberg cited a climatologist’s estimate, reported in the Los Angeles Times, that more than 80 percent of the region’s rainfall ends up diverted from urban areas in Southern California into the Pacific Ocean.

Recycling much of that water, the senators said, would help with landscape and agricultural irrigation and reduce the need for environmentally damaging diversions of water from the Bay-Delta watershed.

Weiner called the bill’s water-saving goals “aggressive and attainable.”

Hertzberg spokeswoman Katie Hanzlik said the bill probably will be discussed in April in the Senate Natural Resources and Water Committee, chaired by Sen. Henry Stern, D-Canoga Park, or the Senate Environmental Quality Committee, chaired by Sen. Ben Allen, D-Santa Monica — or possibly in both committees.

Heather Engel, a spokeswoman for the Association of California Water Agencies, which opposed Hertzberg’s 2015 bill, said the association would wait until the bill goes to a committee before taking a position on it.